Regex Splitting with Negative Lookbehind

Question

The string I am trying to split:

string1, string2, string\,3, string4

I want to split the above string on each comma, except when the comma is escaped with a backslash.

I am unable to utilize negative lookbehind in my JavaScript.

My attempt:

var splits = "string1, string2, string\,3, string4".split("(?<!\\\\),");

None of the commas are being recognized.

Potential solutions: after research, I stumbled across this SO question. However, I don't understand the workarounds well enough to change the above code to the replace the use case.

What should the output look like for this input: `"foo\\, bar"`? (ie. when you escape the escape character). Or this: `"foo\\\, bar"`? — Halcyon, Jun 06 '17 at 15:20
Do you also need to get empty matches? Like in `foo,,bar` => `['foo', '', 'bar']`? — Wiktor Stribiżew, Jun 06 '17 at 15:22
Is your input really `string\,3,` or rather `string3\,`? That second comma is really there in string3? Otherwise, `(?<!\\),` — Shawn Mehan, Jun 06 '17 at 15:35
Yes I wanted empty matches. The output should look like: "string1 " "string2 " "string\,3 " "string4" — J Aronson, Jun 06 '17 at 22:55

score 5 · Accepted Answer · answered Jun 06 '17 at 15:40

You may use

s.match(/(?:[^,\\]|\\.)+/g)

See the regex demo. It will match 1 or more chars other than comma and backslash, or any char that is escaped with a literal backslash.

Note that the string literal should have a double backslash to define a literal backslash.

var splits = "string1, string2, string\\,3, string4".match(/(?:[^,\\]|\\.)+/g);
console.log(splits);

Regex Splitting with Negative Lookbehind

1 Answers1